Multi-layer adhesives and methods for bonding orthodontic appliances to tooth structure

ABSTRACT

The present invention provides multi-layer adhesives and methods that are useful for bonding orthodontic appliances to a tooth structure. The multi-layer adhesives can be precoated on an orthodontic appliance, or alternatively, they can be provided on an adhesive delivery system for transfer to an orthodontic appliance. The multi-layer adhesives and methods preferably provide a useful balance of properties for bonding orthodontic appliances to the tooth structure.

BACKGROUND

Orthodontic treatment involves movement of malpositioned teeth toorthodontically correct positions. Tiny orthodontic appliances known asbrackets are connected to exterior surfaces of the patient's teeth, andan archwire is placed in a slot of each bracket. The archwire forms atrack to guide movement of the teeth to desired positions for correctocclusion. End sections of the archwire are often received in appliancesknown as buccal tubes that are fixed to the patient's molar teeth. Inrecent years it has become common practice to use adhesives to bondorthodontic appliances to the surface of the tooth, using either director indirect methods.

For many years, it was common practice to apply orthodontic adhesive tothe base of the appliance immediately before the appliance was placed onthe tooth. In some instances, a quantity of adhesive was dispensed ontoa mixing pad or dispensing well, and a small spatula or other handinstrument was then used to apply a small dab of adhesive to eachappliance. In other instances, a quantity of adhesive was dispensed froma syringe directly onto the base of the appliance.

Adhesive precoated brackets are known and offer significant advantagesto the orthodontist. Adhesive precoated brackets have a bonding baseupon which the manufacturer may apply a precise quantity of adhesivesuch as a photocurable adhesive. In direct bonding methods, when it isdesired to mount the bracket on a tooth, the bracket is simply removedfrom the package and placed directly onto the tooth. For indirectbonding methods, brackets are removed from the package and placed, forexample, on a replica plaster or “stone” model of the patient's dentalarch to provide a custom base for later mounting on the patient's tooth,commonly using a transfer tray.

In addition to good handling properties and adequate adhesion,practitioners often desire that photocurable adhesives provide otherdesirable functional properties, including, for example, sustainedfluoride release. In many applications, it is also desirable that theadhesive have adequate hydrophilicity or moisture tolerance, asindicated, for example, by the ability of the adhesive to absorb wateror saliva, and/or the ability to provide an adequate bond under moistconditions.

Orthodontic brackets precoated with an adhesive are commonly sold with aflexible release substrate in contact with the adhesive. However, manyrelease substrates are not suitable for use with all adhesives. Forexample, when soft, tacky, less viscous, hydrophilic adhesives are used,it has been found that a portion of the adhesive is sometimes left onthe release substrate when an attempt is made to lift the appliance fromthe container and detach the adhesive from the release substrate. Inthose instances, sufficient adhesive may not remain on the bracket toprovide adequate bond strength to retain the bracket on the tooth duringthe course of orthodontic treatment. Moreover, adhesives having arelatively low viscosity tend to slowly flow across the releasesubstrate and from the space beneath the bracket over extended periodsof time, creating bracket removal and/or liner release problems.

Additionally, when soft, tacky, less viscous adhesives are used withconventional adhesive precoated appliance packages, the shape of theadhesive may distort as the appliance is lifted from the container. Insome instances, detaching the adhesive from the release substrate mayalter the configuration of the adhesive, resulting in unsatisfactorydirect bonding unless additional steps are undertaken to shift theadhesive by hand back to its original, pillow-like shape. For example,when lifting an appliance from the container, some of the adhesive maybe shifted to one side of the appliance base, such that the oppositeside of the base does not have a satisfactory amount of adhesive forbonding. If the appliance is secured to a tooth structure in such amanner that a void space is present between a portion of the base andthe opposed tooth surface, the void space may result in premature,spontaneous debonding of the appliance from the tooth, a nuisance thatis best avoided. Furthermore, in some instances the void space canestablish a pocket that receives food and debris, facilitating theformation of caries.

Presently, there is a need in the art for adhesives and methods thatprovide a balance of properties and characteristics that are desired bythe practitioner.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a packaged article. Thepackaged article includes: an orthodontic appliance having a base forbonding the appliance to a tooth structure; a first hardenable adhesivelayer and a second hardenable adhesive layer, each extending across atleast a portion of the base of the appliance; and a container at leastpartially surrounding the orthodontic appliance having the first andsecond layers thereon. Each of the adhesive layers may independently bepatterned or non-patterned. Each of the adhesive layers mayindependently include, for example, light cure or chemical cureadhesives. Optionally, one or more additional hardenable adhesivelayers, which may be in contact with a release substrate, extend acrossat least a portion of the first or second layers. In one embodiment, thefirst and second layers are not in contact with a release substrate. Inanother embodiment, the appliance is suspended in the package.

In another aspect, the present invention provides an article including:an orthodontic appliance having a base for bonding the appliance to atooth structure; and a first hardenable adhesive layer and a secondhardenable adhesive layer, each extending across at least a portion ofthe base of the appliance, wherein at least one of the first or secondadhesive layers includes a photobleachable dye, and wherein the at leastone adhesive has an initial color prior to exposure to actinic radiationand a final color subsequent to exposure to actinic radiation, theinitial color being different than the final color. Optionally, one ormore additional hardenable adhesive layers extend across at least aportion of the first or second layers. Preferably, at least one of thefirst or second layers further includes a hardener including asensitizing compound different from the photobleachable dye.

In another aspect, the present invention provides an article including:an orthodontic appliance having a base for bonding the appliance to atooth structure; a first hardenable adhesive layer extending across atleast a portion of the base of the appliance and covering a first area;and a second hardenable adhesive layer extending across at least aportion of the base of the appliance and covering a second area, whereinthe second area is different than the first area. In some embodiments,the first area is coextensive with the base of the appliance. In someembodiments, the second area is smaller than the first area. In someembodiments, one of the areas is proximate the center of the base of theappliance. In some embodiments, one of the areas is proximate theperiphery of the base of the appliance. Optionally, one or moreadditional hardenable adhesive layers extend across at least a portionof the first or second layers.

In another aspect, the present invention provides an orthodonticadhesive delivery system or a packaged orthodontic adhesive deliverysystem. The system includes: a substrate including an adhesive transferarea; a first hardenable adhesive layer extending across at least aportion of the adhesive transfer area; and a second hardenable adhesivelayer extending across at least a portion of the first hardenableadhesive layer. In some embodiments, at least one of the first or secondlayers is in the form of dots or lines. Optionally, one or moreadditional hardenable adhesive layers extend across at least a portionof the first or second hardenable adhesive layer.

In another aspect, the present invention provides an orthodonticadhesive delivery or a packaged orthodontic adhesive delivery system.The system includes: a substrate including an adhesive transfer area;and a first hardenable adhesive layer and a second hardenable adhesivelayer, each extending across at least a portion of the adhesive transferarea, with the proviso that the first and second hardenable layers arenot different parts of a multi-part, chemical cure adhesive.

The present invention also provides methods of making and usingprecoated orthodontic devices and orthodontic adhesive delivery systems.

Definitions

As used herein, “orthodontic appliance” refers to any device intended tobe bonded to a tooth structure, including, but not limited to,orthodontic brackets, buccal tubes, bite openers, buttons, and cleats.Thus, the term “orthodontic appliance” encompasses orthodontic bands.The appliance has a base for receiving adhesive and it can be a flangemade of metal, plastic, ceramic, and combinations thereof.Alternatively, the base can be a custom base formed from cured adhesivelayer(s) (i.e., single or multi-layer adhesives).

As used herein, a “packaged” article refers to an orthodontic applianceor card that is received in a container. Preferably, the containerprovides protection from environmental conditions including, forexample, moisture and light.

As used herein, a “release” substrate refers to a substrate in contactwith an article that is removed from the article before or during use ofthe article.

As used herein, a “multi-layer” adhesive refers to an adhesive havingtwo or more layers.

As used herein, a “layer” refers to a discontinuous (e.g., a patternedlayer) or continuous (e.g., non-patterned) material extending across allor a portion of a different material. A layer may be of uniform orvarying thickness.

As used herein, a “patterned layer” refers to a discontinuous layer inwhich the material of the patterned layer extends across only selectedportions of another material.

As used herein, a “non-patterned layer” refers to a continuous layer inwhich the material of the non-patterned layer extends across an entireportion of another material.

In general, a layer “extending across” or “attached to” another layer isintended to be broadly interpreted to optionally include one or moreadditional layers between the two layers.

As used herein, “hardenable” is descriptive of a material that can becured or solidified, for example, by heating to remove solvent, heatingto cause polymerization, chemical cross-linking, radiation-inducedpolymerization, or crosslinking.

As used herein, “hardener” means a system that initiates hardening of aresin. A hardener may include, for example, a polymerization initiator.

As used herein, “photobleachable” refers to loss of color upon exposureto actinic radiation.

As used herein, “filler” means a particulate material (e.g., aninorganic oxide) in dry powder form capable of being dispersed in aresin. For example, a dental composite preferably includes a powderdispersed in a resin.

As used herein, the term “(meth)acrylate” is a shorthand reference toacrylate, methacrylate, or combinations thereof, and “(meth)acrylic” isa shorthand reference to acrylic, methacrylic, or combinations thereof.

As used herein, the chemical term “group” allows for substitution.

As used herein, “a” or “an” means one or more.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of an orthodontic appliance having amulti-layer adhesive on the base thereof.

FIG. 2 is a side view of the orthodontic appliance of FIG. 1.

FIGS. 3-6 are bottom views of exemplary embodiments of articles (e.g.,orthodontic appliances or adhesive delivery systems) having multi-layeradhesives thereon.

FIG. 7 is a perspective view of a packaged article illustrating anorthodontic appliance having a multi-layer adhesive coated on the basethereof in a container in which the cover has been partially opened.

FIG. 8 is an enlarged side cross-sectional view showing the act ofapplying a dental appliance to a patient's tooth using a placementdevice used with an indirect bonding method.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides multi-layer adhesives (i.e., two or morehardenable adhesive layers) and methods using the multi-layer adhesivesfor bonding orthodontic appliances to a tooth structure. In someembodiments, the multi-layer adhesives are provided precoated on anorthodontic appliance. In other embodiments, the multi-layer adhesivesare provided on an orthodontic adhesive delivery system, and aresubsequently transferred to an orthodontic appliance. The multi-layeradhesives are preferably provided as packaged articles, with or withoutrelease substrates, such as those described, for example, in U.S. Pat.No. 6,183,249 (Brennan et al.).

In FIGS. 1 and 2, an exemplary orthodontic appliance is designated bythe numeral 10 and is a bracket, although other appliances such asbuccal tubes, buttons and other attachments are also possible. Theappliance 10 includes a base 12. The appliance 10 also has a body 14that extends outwardly from the base 12. Base 12 can be a flange made ofmetal, plastic, ceramic, and combinations thereof. Alternatively, thebase 12 can be a custom base formed from cured adhesive layer(s) (i.e.,single or multi-layer adhesives). Tiewings 16 are connected to the body14, and an archwire slot 18 extends through a space between the tiewings16. The base 12, the body 14, and tiewings 16 may be made of any one ofa number of materials suitable for use in the oral cavity and havingsufficient strength to withstand the correction forces applied duringtreatment. Suitable materials include, for example, metallic materials(such as stainless steel), ceramic materials (such as monocrystalline orpolycrystalline alumina), and plastic materials (such asfiber-reinforced polycarbonate). Optionally, the base 12, the body 14,and the tiewings 16 are integrally made as a unitary component.

A multi-layer adhesive 20 extends across the base 12 of the appliance10. The multi-layer adhesive 20 serves in whole or at least in part tosecurely fix the appliance 10 to the patient's tooth by a bond havingsufficient strength to resist unintended detachment from the toothduring the course of treatment. Preferably, the multi-layer adhesive 20is applied by the manufacturer to the base 12 of the appliance 10.

The multi-layer adhesive 20 illustrated in FIGS. 1 and 2 includesadhesive layer 22 extending across base 12, and adhesive layer 24extending across base 12 and adhesive layer 22. It should be understoodthat multi-layer adhesive 20 can include additional layers that are notillustrated in FIGS. 1 and 2. Layers 22 and 24 are layers of differentadhesives that may or may not cover the same area. Layers 22 and 24 mayindependently be discontinuous (e.g., a patterned layer) or continuous(e.g., non-patterned) material extending across all or a portion ofanother material.

Adhesive layers 22 and 24 may differ in properties including, forexample, chemical composition; viscosity; hydrophilicity as disclosed,for example, in U.S. Pat. No. 6,126,922 (Rozzi et al.); thickness;curing times; curing mechanisms; color; change in color upon curing;enzyme release; fluoride release; bond strengths upon curing; fillerloading; filler types; and pH (as disclosed, for example, in PCTInternational Publication No. WO 00/69393 (Brennan et al.).

Adhesive layers 22 and 24 may each be a liquid, a paste, or a solidmaterial that is converted into a liquid or paste during the bondingprocedure. Suitable compositions include composites, compomers, glassionomers and resin-modified glass ionomers. Examples of light-curableadhesives include Transbond XT brand and Transbond LR brand adhesivesfrom 3M Unitek. Examples of chemical curing adhesives include Sondhibrand Rapid-Set indirect bonding adhesive, Unite brand adhesive, Concisebrand adhesive and Multi-Cure brand glass ionomer cement from 3M Unitek.

Compositions useful in adhesive layers of the present invention are wellknown to one of skill in the art. Useful compositions include, forexample, both light cure and chemical cure orthodontic adhesives. Insome embodiments, the compositions are preferably fluoride releasingadhesives, self etching adhesives, self priming adhesives,color-changing adhesives, and combinations thereof.

Optionally, the composition is an adhesive that falls in one of thefollowing classes in accordance with the practitioner's preferences fortooth treatment:

Class I: An adhesive that requires both etching of tooth enamel (using,for example, phosphoric acid or a bisphosphonic acid) and a separateapplication of a primer to the tooth enamel.

Class II: An adhesive that requires etching (using, for example,phosphoric acid, a bisphosphonic acid or self-etching primer) but not aseparate application of primer.

Class III: An adhesive that requires no treatment of the teeth otherthan cleaning.

Possible primers for use with class I adhesives include orthodonticprimers such as Transbond MIP brand primer and Transbond XT brand primerfrom 3M Unitek and Ortho Solo brand primer from Ormco Corporation.Optionally, the primer may include a photobleachable dye to ensureadequate coverage of the primer on the teeth, a small amount offluoroalumina silicate glass (“FAS” glass) for providing fluoriderelease during treatment, a small amount of fumed silica for rheologycontrol purposes, and/or a small amount of silanated quartz filler forenhanced fracture toughness.

Suitable class II adhesives include the adhesives mentioned above. Thelayer first contacting the tooth can be replaced by a self-etchingprimer such as Transbond Plus SEP brand primer from 3M Unitek.Optionally, the self-etching primer could incorporate the optionalfeatures described above for the class I adhesive.

Suitable class III adhesives avoid the need for etching and priming theteeth and may be referred to as “self-adhesive” compositions. With theseadhesives, the practitioner need only clean the teeth prior toapplication of the dental appliance in a typical bonding procedure.Suitable class III adhesives may include an acid component selected froma methacrylate phosphate (e.g., mono-HEMA phosphate, di-HEMA phosphate,glycerol dimethacrylate (GDMA) phosphate), a solution of a bisphosphonicacid in water or other solvent, and a bisphosphonic acid in powder form(using water for ionizing that is left on the teeth after tooth prophyand rinse). Other class III adhesives may include an ethylenicallyunsaturated component with acid functionality, an ethylenicallyunsaturated component without acid functionality, an initiator system,and a filler. Optionally a class III adhesive may be essentially free ofwater. Examples of class III adhesives have been previously described,e.g. in pending U.S. Provisional Pat. Application No. 60/494,603 filedAug. 12, 2003.

The class III adhesives described above can optionally incorporatefillers (e.g., a glass ionomer-type filler that binds the water in theusual glass ionomer setting reaction). In addition, any of the class IIIadhesives described above may incorporate the optional featuresdescribed in connection with class I adhesives.

Adhesives useful in the present invention may optionally includecomponents such as fluoride releasing agents as described, for example,in U.S. Pat. No. 3,814,717 (Wilson et al.) and U.S. Pat. No. 6,126,922(Rozzi et al.); adhesive enhancing agents (e.g., titanites, zirconates)as disclosed, for example, in PCT International Publication No. WO00/69393 (Brennan et al.); fillers; micro fillers; enzyme releasingagents; rheology enhancing agents; photobleachable dyes; andcombinations thereof.

In some embodiments, one or more adhesives in multi-layer adhesives ofthe present invention preferably have an initial color remarkablydifferent than dental structures. Color is preferably imparted to thecomposition through the use of a photobleachable dye. The compositionpreferably includes at least 0.001% by weight photobleachable dye, andmore preferably at least 0.002% by weight photobleachable dye, based onthe total weight of the composition. The composition preferably includesat most 1% by weight photobleachable dye, and more preferably at most0.1% by weight photobleachable dye, based on the total weight of thecomposition. The amount of photobleachable dye may vary depending on itsextinction coefficient, the ability of the human eye to discern theinitial color, and the desired color change.

The color formation and bleaching characteristics of the photobleachabledye varies depending on a variety of factors including, for example,acid strength, dielectric constant, polarity, amount of oxygen, andmoisture content in the atmosphere. However, the bleaching properties ofthe dye can be readily determined by irradiating the composition andevaluating the change in color. Preferably, at least one photobleachabledye is at least partially soluble in a hardenable resin.

Exemplary classes of photobleachable dyes are disclosed, for example, inU.S. Pat. No. 6,331,080 (Cole et al.), U.S. Pat. No. 6,444,725 (Trom etal.), and 6,528,555 (Nikutowski et al.). Preferred dyes include, forexample, Rose Bengal, Methylene Violet, Methylene Blue, Fluorescein,Eosin Yellow, Eosin Y, Ethyl Eosin, Eosin bluish, Eosin B, Erythrosin B,Erythrosin Yellowish Blend, Toluidine Blue, 4′,5′-Dibromofluorescein,and combinations thereof.

The color change in the adhesives is initiated by light. Preferably, thecomposition's color change is initiated using actinic radiation using,for example, a dental curing light which emits visible or near infrared(IR) light for a sufficient amount of time. The mechanism that initiatesthe color change in the compositions of the invention may be separatefrom or substantially simultaneous with the hardening mechanism thathardens the resin. For example, a composition may harden whenpolymerization is initiated chemically (e.g., redox initiation) orthermally, and the color change from an initial color to a final colormay occur subsequent to the hardening process upon exposure to actinicradiation.

The change in composition color from an initial color to a final coloris preferably quantified by a Color Test as described below. Using theColor Test, a value of ΔE* is determined, which indicates the totalcolor change in a 3-dimensional color space. The human eye can detect acolor change of approximately 3 ΔE* units in normal lighting conditions.The dental compositions of the present invention are preferably capableof having a color change, ΔE*, of at least 10; more preferably, ΔE* isat least 15; most preferably ΔE* is at least 20.

Each layer of the multi-layer adhesive can be patterned ornon-patterned. The layers can cover the same or different areas of theappliance or adhesive delivery system. One layer can cover none of,partially cover, or fully cover another adhesive layer. Patterned layersmay be in forms including, for example, lines, dots, squares, circles,and combinations thereof. Layers can be of uniform or varying thickness.

FIGS. 3-6 are bottom views of exemplary embodiments of articles 30(e.g., orthodontic appliances or adhesive delivery systems) havingmulti-layer adhesives 32 thereon. If article 30 is an orthodonticappliance, then numeral 32 represents the base of the appliance. Base 32can be a flange made of metal, plastic, ceramic, and combinationsthereof. Alternatively, base 32 can be a custom base formed from curedadhesive layer(s) (i.e., single or multi-layer adhesives). If article 30is an adhesive delivery system, then numeral 32 represents the adhesivetransfer area of a substrate.

Referring to FIGS. 3-5, in some embodiments, adhesive layer 34 mayrepresent a continuous layer that is coextensive with the area of thebase or adhesive transfer area 32. Alternatively, in some embodiments,adhesive layer 34 may represent a discontinuous layer that covers onlythe lighter stipled area.

In the exemplary embodiments illustrated in FIGS. 3-5, adhesive layer 36represents a discontinuous layer extending across only the portions ofthe base or adhesive transfer area 32 indicated by the darker stipledareas. Referring to FIG. 3, discontinuous adhesive layer 36 is apatterned layer represented as a pattern of darker stipled dots.Referring to FIG. 4, discontinuous adhesive layer 36 is represented asthe single darker stipled “donut hole” area. Referring to FIG. 5,discontinuous adhesive layer 36 is represented as the single darkerstipled square area.

In embodiments where adhesive layer 34 represents a continuous layer,adhesive layer 36 extends across the portions of layer 34 indicated bythe darker stipled areas. Alternatively, in embodiments where adhesivelayer 34 represents a discontinuous layer that covers only the lighterstipled areas, adhesive layer 36 may extend across the portions of baseor adhesive transfer area 32 indicated by the darker stipled areas.

In the exemplary embodiment illustrated in FIG. 6, adhesive layers 34and 36 are both discontinuous layers. Adhesive layer 34 extends acrossthe portions of base or adhesive transfer area 32 indicated by thelighter stipled areas as a pattern of dots. Similarly, adhesive layer 36extends across the portions of base or adhesive transfer area 32indicated by the darker stipled areas as a pattern of dots. In theembodiment illustrated in FIG. 6, none of the dots of adhesive layer 36extend across adhesive layer 34. However, in other embodiments (notillustrated), dots or portions of dots of adhesive layer 36 can extendacross adhesive layer 34. Alternatively, both of dots 34 and 36 could belocated on base or adhesive transfer area 32 and contact each other.When article 30 is an adhesive delivery system and numeral 32 representsthe adhesive transfer area of a substrate, then either (i) adhesivelayers 34 and 36 are not different parts of a multi-part, chemical cureadhesive, or (ii) another layer (not illustrated) extends across atleast a portion of adhesive layer 34 or 36.

In some embodiments, the multi-layer adhesives and methods describedherein offer advantages over adhesives known in the art. Benefitspreferably include increased bonding efficiency and/or a decreasednumber of bonding steps. Preferably, the bond strength is increased,thereby reducing the incidence of bond failures. For example, a firstlayer may be selected for properties specific to the bracket being used(e.g., size and construction of the base), a second layer may beselected to provide the desired bond strength for the specificapplication (posterior or cuspid/bicuspid applications), and a thirdlayer may be selected to conform with the specific tooth surface towhich the bracket will be attached.

In some embodiments, the orthodontic appliances described herein may beused without priming the tooth, thereby decreasing the number of stepsrequired in the bonding procedure and saving both the clinician and thepatient time and money. Other advantages include, for example, theopportunity to tailor overall adhesive properties by using a combinationof adhesives with different properties in the multi-layer construction.

In some embodiments, the adhesive layers can be patterned to provide fordesired properties including, for example, easier clean-up and flashremoval. For example, a layer can be thicker around the periphery of thebase to provide for easier flash removal, and/or the layer around theperiphery of the base can include a color-changing adhesive.Alternatively, the layer near the middle of the base can include anadhesive that cures readily with less light than would be available atthe periphery of the base.

In some embodiment, one or more of the above features can be combined.For example, the combination of an adhesive having increased moisturetolerance can be combined with a patterned adhesive that changes colorupon curing to provide a multi-layer adhesive that has a reducedincidence of bond failure upon bonding to a moist surface, with easierclean-up.

Multi-layer adhesives as described herein can be prepared by methodsknown to one of skill in the art. Suitable methods include, for example,applying, dispensing, or printing the layers of adhesive on an applianceor a substrate. Multiple layers may be applied simultaneously orsequentially.

A useful method for applying multiple layers of adhesive on anorthodontic appliance or a substrate includes, for example, usingautomated fluid dispensing systems such as those available under thetrade designation AUTOMOVE from Asymtek (Carlsbad, Calif.). Suchautomated fluid dispensing systems are useful for dispensing bothpatterned and non-patterned layers. Other useful systems include, forexample, piston dispensing systems and multiple resolution fluidapplicators as described, for example, in U.S. Pat. No. 6,513,897(Tokie).

Once the multi-layer adhesive has been applied to an orthodonticappliance or a substrate, the appliance or substrate can conveniently bepackaged in a container. Exemplary containers are well known in the artand are disclosed, for example, in U.S. Pat. No. 5,172,809 (Jacobs etal.) and U.S. Pat. No. 6,089,861 (Kelly et al.).

Referring to FIG. 7, an exemplary embodiment of packaged article 40including orthodontic appliance 42 having a multi-layer adhesive coatedon the base thereof is shown. Package 44 includes container 46 and cover48. Cover 48, which is releasably connected to container 46 as initiallyprovided, is peeled from container 46 to open the package for removal oforthodontic appliance 42. In FIG. 7, cover 48 has been peeled back fromcontainer 46 to partially open package 44.

In preferred embodiments, the package provides excellent protectionagainst degradation of the multi-layer adhesives (e.g., photocurablematerials), even after extended periods of time. Such containers areparticularly useful for protecting dyes that impart a color changingfeature to the multi-layer adhesives. Such containers preferablyeffectively block the passage of actinic radiation over a broad spectralrange, and as a result, the multi-layer adhesive does not prematurelylose color during storage.

In preferred embodiments, the package includes container 46 comprising apolymer and metallic particles. As an example, container 46 may be madeof polypropylene that is compounded with aluminum filler or receives analuminum powder coating as disclosed, for example, in U.S. Pat.Application Publication No. 2003/0196914 A1 (Tzou et al.). Thecombination of polymer and metallic particles provides a highlyeffective block to the passage of actinic radiation to color changingdyes, even though such dyes are known to be highly sensitive to light.Such containers also exhibit good vapor barrier properties. As a result,the rheological characteristics of the multi-layer adhesives are lesslikely to change over extended periods of time. For example, theimproved vapor barrier properties of such containers provide substantialprotection against degradation of the handling characteristics ofmulti-layer adhesives so that the adhesives do not prematurely cure ordry or become otherwise unsatisfactory. Suitable covers 48 for suchcontainers can be made of any material that is substantially opaque tothe transmission of actinic radiation so that the multi-layer adhesivedoes not prematurely cure. Examples of suitable materials for cover 48include laminates of aluminum foil and polymers. For example, thelaminate may comprise a layer of polyethyleneterephthalate, adhesive,aluminum foil, adhesive and oriented polypropylene.

In some embodiments, a packaged orthodontic appliance including amulti-layer adhesive thereon may include a release substrate asdescribed, for example, in U.S. Pat. No. 6,183,249 (Brennan et al.).

In other embodiments, a packaged orthodontic appliance including amulti-layer adhesive thereon may not include a release substrate. In oneembodiment, the package includes a substrate with at least one recesswith an interior surface. The package includes a means for positioningthe orthodontic appliance inside the recess such that the adhesivelayers do not separate from the appliance upon removal of the appliancefrom the recess. Preferably, the package further includes a cover forthe recess and a means for maintaining the cover in contact with thesubstrate, wherein the means for positioning the orthodontic applianceincludes means suspending the appliance in the recess such that theadhesive layers do not contact the interior surface of the recess. Suchpackages are disclosed, for example, in U.S. Pat. No. 5,172,809 (Jacobset al.).

In another embodiment the orthodontic appliance has a base for bondingthe appliance to a tooth structure and a body extending from the baseand at least two opposed tiewings extending away from the body. The baseand at least one of the tiewings extend past the body in a gingivaldirection and present a gingival recess. The base and at least one otherof the tiewings extend past the body in an occlusal direction andpresent an occlusal recess. The package includes a carrier having a pairof arms extending toward each other. Each of the arms has an outer endsection, with the outer end sections being spaced apart from each otherand presenting a channel therebetween. The orthodontic appliance islocated in the channel and is supported by the arms with one of theouter end sections extending into the occlusal recess and the other ofthe outer end sections extending into the gingival recess. Suchorthodontic appliances and packages are described, for example, in U.S.Pat. No. 6,089,861 (Kelly et al.).

In some embodiments, a packaged article can include a set of orthodonticappliances, wherein at least one of the appliances has a multi-layeradhesive thereon. In some embodiments, some or all of the appliances mayhave different adhesives or multi-layer adhesives thereon. For example,a packaged article may include both brackets and buccal tubes, and thebrackets may each have the same or different adhesive or multi-layeradhesive thereon as the buccal tube. This provides for flexibility fortailoring adhesive properties for the desired end use. For example, morehydrophilic adhesives may be used for posterior appliances, softeradhesives may be used for appliances having larger bonding bases (e.g.,posterior appliances), and adhesives capable of developing higher bondstrengths may be used for cuspid and bicuspid appliances. Additionalexamples of articles and sets of appliances are described in applicant'spending U.S. patent application Ser. No. 10/742,561 entitled “PACKAGEDORTHODONTIC ASSEMBLY WITH ADHESIVE PRECOATED APPLIANCES” and filed oneven date herewith. Packaged orthodontic appliances are described, forexample, in U.S. Pat. Application Publication No. 2003/0196914 A1 (Tzouet al.) and U.S. Pat. No. 4,978,007 (Jacobs et al.), U.S. Pat. No.5,015,180 (Randklev), U.S. Pat. No. 5,328,363 (Chester et al.), and U.S.Pat. No. 6,183 249 (Brennan et al.).

In direct bonding methods, the orthodontic appliance having amulti-layer adhesive thereon is removed from the package and placeddirectly on the desired tooth surface and allowed to cure.

In some embodiments of the present invention, an adhesive deliverysystem is provided that includes a multi-layer adhesive extending acrossat least a portion of an adhesive transfer area of a substrate. Thesubstrate may optionally be provided as a packaged article. Afterremoving the substrate having the multi-layer adhesive thereon from thepackage, if present, the multi-layer adhesive may be transferred to thebase of an orthodontic appliance, which can then be bonded to a toothstructure either through direct or indirect methods. Exemplary adhesivedelivery systems are described, for example, in U.S. Pat. No. 6,213,767(Dixon et al.).

The multi-layer adhesives disclosed in the present application may alsobe used for indirect bonding methods. For indirect bonding methods,orthodontic appliances are removed from the package and placed, forexample, on a replica plaster or “stone” model of the patient's dentalarch to provide a custom base for later mounting on the patient's toothstructure, commonly using a placement device. In one embodiment, theorthodontic appliances have multi-layer adhesives on the bases thereofto bond to the replica plaster or “stone” model, to provide the custombase. Exemplary indirect bonding methods are described, for example, incopending U.S. patent application Ser. No. 10/678,286, filed Oct. 3,2003.

In another embodiment of indirect bonding methods, the orthodonticappliance provided in the placement device may have multi-layeradhesives on the custom bases for bonding to the patient's teeth.Referring to FIG. 8, the placement device 50 (comprising shell 60,matrix material 70, and appliances 80) is shown in cross-sectional view.The appliances 80 include custom bases 82 that are coated withmulti-layer adhesive 84. The placement device 50 is then placed in apackage by the manufacturer and shipped to the practitioner's office.

Once the patient has returned to the office, bonding procedure isundertaken. Preferably, any tooth preparation steps are carried outbefore the packaged placement device is opened. In this manner, themulti-layer adhesive 84 is not unduly exposed to ambient light or air.After any tooth preparation steps are completed, the package is openedand placement device 50 is removed from the package.

The shell 60 is then positioned over the corresponding teeth and seated,optionally with a swinging, hinge-type motion. In FIG. 8, the patient'stooth is designated by the numeral 90. Since the shape of the cavity ofthe matrix material 70 matches the shape of the underlying teeth, theappliances 80 are simultaneously seated against the underlying teeth 90at precisely the same locations corresponding to the previous positionof the appliances 80 on the replica. Preferably, pressure is thenapplied to the occlusal, labial and buccal surfaces of the shell 60until such time as the multi-layer adhesive 84 has sufficientlyhardened. Optionally, finger pressure may be used to firmly press theappliances 80 against the enamel surfaces of the patient's teeth 90.

Once the multi-layer adhesive 84 has hardened, the shell 60 is carefullyremoved from the patient's dental arch. Preferably, the shell 60 isfirst separated from the matrix material 70, which remains in place overthe dental arch along with the appliances 80. Next, the matrix material70 is detached from the appliances 80. Optionally, a hand instrumentsuch as a scaler may be used to help hold each appliance 80 against thesurface of the respective tooth 90 of the patient as the matrix material70 is peeled away from the appliances 80. However, in instances where arelatively soft matrix material is employed or otherwise readilyreleases from the appliances 80, the use of a scaler to help avoidfracturing the fresh adhesive bond is optional. As another option, theshell 60 may be separated from the matrix material 70 before themulti-layer adhesive 84 has hardened. This option is particularly usefulwhen the multi-layer adhesive 84 includes a light-curable adhesive. Oncethe matrix material 70 has been detached from the appliances 80, anarchwire is placed in the slots of the appliances 80 and ligated inplace.

EXAMPLES

The following examples are given to illustrate, but not limit, the scopeof this invention. Unless otherwise indicated, all parts and percentagesare by weight and all molecular weights are weight average molecularweight.

TABLE 1 Abbreviations, Descriptions, and Sources of Materials HEMA2-Hydroxyethyl methacrylate (CAS No. 868-77-9) Adhesive A Acolor-changing, light cure adhesive similar to that described in U.S.Pat. Application Publication No. 2003/0198914 A1 (Brennan et al.),Example 10. Adhesive B A light cure adhesive similar to that describedin PCT International Publication No. WO 00/69393 (Brennan et al.), aslisted in Table 2, Sample A. Transbond LR A light cure adhesiveavailable under the trade designation Transbond LR from 3M Unitek(Monrovia, CA) Transbond MIP A moisture insensitive primer availableunder the trade designation Transbond MIP from 3M Unitek (Monrovia, CA)APC II A light cure adhesive coated appliance available under the tradedesignation APC II from 3M Unitek (Monrovia, CA) Transbond A selfetching primer available under the trade Plus SEP designation TransbondPlus from 3M Unitek (Monrovia, CA) Transbond XT A light cure adhesiveavailable under the trade designation Transbond XT from 3M Unitek(Monrovia, CA)Bond Strength Test Method

Bond strength was tested by adhering adhesive coated orthodonticbrackets to bovine teeth. The brackets used were either ceramic bracketshaving bases with protruding alumina particles for contact withadhesive, or metal brackets having either mesh or integral molded bases.Brackets commercially available with precoated adhesive were used asreceived. For brackets without precoated adhesive, the brackets weretreated with an adhesive as described herein below. The adhesive sampleswere applied either by syringe or using an automated fluid dispensingsystem available under the trade designation AUTOMOVE A-403 from Asymtek(Carlsbad, Calif.).

In some examples, the bovine teeth were first cleaned with a pumiceaqueous slurry and rinsed. The teeth were then etched with 37%phosphoric acid etching solution, rinsed with water and dried withmoisture-free and oil-free air. The teeth were then treated with amoisture insensitive primer available under the trade designationTRANSBOND MIP from 3M Unitek (Monrovia, Calif.), following themanufacturer's instructions.

Alternately, in other examples, the pumiced teeth were treated with aself etching primer available under the trade designation TRANSBOND PlusSEP from 3M Unitek (Monrovia, Calif.), following the manufacturer'sinstructions. The brackets with applied adhesive were then seated ontothe teeth and pressed firmly to extrude any excess adhesive. The excesswas cleaned away.

The adhesive was then cured according to manufacturers instructionsusing a curing unit available under the trade designation ORTHO Litefrom 3M Unitek (Monrovia, Calif.) (e.g., 10 seconds through the bracketfor brackets available under the trade designation TRANSCEND from 3MUnitek (Monrovia, Calif.)). The samples of teeth and bonded bracketswere stored overnight in 37° C. water.

Bond strength testing was performed by engaging a 0.50-mm roundstainless steel wire loop under the occlusal tie wings. Using auniversal load frame available from MTS Systems Corporation (EdenPrairie, Minn.), a load was applied in a shear/peel mode until debondingof the bracket from the tooth occurred. The wire attached to theuniversal load frame was pulled at a rate of 5 mm/minute. The maximumforce (in units of pounds) was recorded as bond strength per bracket andreported as results of the “dry” tooth condition test.

In a variation of this test method, moisture (in the form of distilledwater by a spray bottle or saliva by a cotton swab) was applied to theetched and/or primed bovine teeth before bonding the adhesive-coatedbrackets to the teeth. The maximum force was recorded as bond strengthper bracket and reported as results of the “wet” tooth condition test.

Color Test

Quantification of initial and bleached color of adhesive samples wasperformed with a portable ultraviolet-visible (UV-Vis) spectrometeravailable under the trade designation EPP2000C from StellarNet, Inc.(Oldsmar, Fla.) equipped with a 400-micron fiber reflectance probe andcolorimeter software available under the trade designation SpectraWizCIELAB from StellarNet, Inc. (Oldsmar, Fla.).

To prepare samples for color measurement, an adhesive sample wasextruded onto a polyester release liner, a metal ring was placed aroundthe adhesive, and a second release liner was placed on top of theadhesive. The resulting construction was then pressed between twoPlexiglas plates with the metal ring controlling the adhesive thicknessto 0.51 mm. With the light source of the spectrometer switched off, theadhesive sample between the two release liners was placed on top of awhite reflectance standard (Part No. RS50, 50-millimeter diameter, Halontype >97% reflectance, 300-1500 nanometers, StellarNet, Inc.). The fiberoptic probe of the spectrometer was positioned 6.3 millimeters above thesample at a 45° angle. Color measurements were taken through the toprelease liner at an exposure time of 1000 milliseconds and with thecenter of the adhesive under the beam. The software captured thereflectance spectrum and converted the input to L*, a* and b* values.The a* value was indicative of the redness of the sample with highernumbers indicative of greater redness.

Cured adhesive samples were prepared in the same manner describedherein, except that the adhesive pressed between the two polyesterrelease liners was cured for 3 minutes in a light curing oven availableunder the trade designation TRIAD 2000 from Dentsply International, Inc.(York, Pa.). The cured adhesive sample with the polyester liners intactwas placed directly onto the white reflectance standard. The lightsource of the spectrometer was switched on and L*, a* and b* values weremeasured as described herein with each reported value representing theaverage of 3 measurements.

Example 1

Upper lateral brackets available as Unitek Miniature Twin V-slot metalbrackets, Cat. No. 017-333 from 3M Unitek (Monrovia, Calif.), werecoated with light cure Adhesive B in an amount sufficient to coat theentire base of the bracket when applied to a tooth. The brackets werebonded to etched bovine teeth using the procedure described herein abovewithout the use of either Transbond MIP or Transbond Plus SEP, resultingin a “dry” tooth condition bond strength of 21.7 MPa with a standarddeviation of 5.7 MPa (45 pounds per bracket with a standard deviation of11.8 pounds per bracket) and a “wet” tooth condition bond strength of9.2 MPa with a standard deviation of 6.6 MPa (19 pounds per bracket witha standard deviation of 13.7 pounds per bracket).

Some of the appliances described in the paragraph herein above weredipped into stabilized HEMA to form multi-layer adhesive coated bracketshaving a layer of HEMA on the adhesive. The multi-layer adhesive coatedbrackets were then bonded to bovine teeth using the procedure describedherein above without the use of either Transbond MIP brand primer orTransbond Plus SEP brand primer, resulting in a “wet” tooth conditionbond strength of 20.3 MPa with a standard deviation of 5.7 MPa (42pounds per bracket with a standard deviation of 11.8 pounds perbracket).

The “wet” tooth condition bond strength for the multi-layer adhesivecoated bracket illustrates that excellent bond strengths can be obtainedwithout separately applying a primer to the tooth. The “wet” toothcondition bond strength for the multi-layer adhesive coated bracket alsoillustrates that excellent bond strengths can be obtained under “wet”tooth conditions. The example also illustrates that low viscosity layers(e.g., the HEMA layer) and/or hydrophilic layers (e.g., the HEMA layer)in contact with the tooth may improve the wetting of the tooth surfaceby the adhesive resulting in increased bond strengths.

Example 2

The single layer and multilayered samples were coated using an automatedfluid dispensing system available under the trade designation AUTOMOVEA-403 from Asymtek (Carlsbad, Calif.).

Universal bicuspid brackets available under the trade designationTRANSCEND from 3M Unitek (Monrovia, Calif.) were coated with acontinuous layer of color-changing, light cure Adhesive A in an amountsufficient to coat the entire base of the bracket when applied to atooth. The coated brackets were bonded to bovine teeth using theprocedure described herein above, resulting in a “dry” tooth conditionbond strength of 7.9 MPa with a standard deviation of 2.7 MPa (20.8pounds per bracket with a standard deviation of 7.2 pounds per bracket).

Some of the universal bicuspid brackets coated with color-changing,light cure Adhesive A as described in the paragraph herein above, werecoated with a second continuous layer of adhesive available under thetrade designation Transbond LR from 3M Unitek (Monrovia, Calif.) in anamount sufficient to coat the entire base of the bracket when applied toa tooth. The multi-layer brackets were bonded to bovine teeth using theprocedure described herein above, resulting in a “dry” tooth conditionbond strength of 10.5 MPa with a standard deviation of 2.2 MPa (27.8pounds per bracket with a standard deviation of 5.9 pounds per bracket).

The example illustrates that low viscosity adhesive (e.g., a TransbondLR layer) in contact with a tooth may improve the wetting of the toothsurface by the adhesive, resulting in increased bond strengths.

Example 3

The samples were coated using an automated fluid dispensing systemavailable under the trade designation AUTOMOVE A-403 from Asymtek(Carlsbad, Calif.).

Universal bicuspid brackets available under the trade designationTRANSCEND from 3M Unitek (Monrovia, Calif.) were coated with acontinuous layer of color-changing, light cure Adhesive A in an amountsufficient to coat the entire base of the bracket when applied to atooth. The coated brackets were bonded to bovine teeth using theprocedure described herein above, resulting in a “dry” tooth conditionbond strength of 7.9 MPa with a standard deviation of 2.7 MPa (20.8pounds per bracket with a standard deviation of 7.2 pounds per bracket).

Universal bicuspid brackets were coated with a continuous layer of aprecoat bracket adhesive available under the trade designation of APC IIfrom 3M Unitek (Monrovia, Calif.) in an amount sufficient to coat theentire base of the bracket when applied to a tooth. The brackets werethen coated with a second continuous layer of color-changing, light cureAdhesive A in an amount sufficient to coat the entire base of thebracket when applied to a tooth. The multi-layer brackets were bonded tobovine teeth using the procedure described herein above, resulting in a“dry” tooth condition bond strength of 12.0 MPa with a standarddeviation of 3.6 MPa (31.6 pounds per bracket with a standard deviationof 9.5 pounds per bracket).

The example illustrates that hydrophobic (APC II) and hydrophiliccolor-changing, light cure Adhesive A can be placed on the same bracket,resulting in increased bond strengths.

Example 4

The samples were coated using an automated fluid dispensing systemavailable under the trade designation AUTOMOVE A-403 from Asymtek(Carlsbad, Calif.).

Universal bicuspid brackets available under the trade designationTRANSCEND from 3M Unitek (Monrovia, Calif.) were coated with a ribbon ofcolor-changing, light cure Adhesive A around the periphery of the baseto form a “donut” shape. A second adhesive available under the tradedesignation APC II form 3M Unitek (Monrovia, Calif.) was applied ontothe center of the “donut” of color-changing, light cure Adhesive A.

The example illustrates that a color-changing “donut” layer that is richin color promotes easy flash clean-up without the need for dye dispersedthroughout all the adhesive(s).

Example 5

Example 4 is repeated except that the color-changing adhesive is alsofluoride-releasing.

The example illustrates that a fluoride rich fluoride-releasing “donut”layer at the bonding surface can offer enhanced fluoride release wheredesired for caries prevention without the need for fluoride releasethroughout all the adhesive(s).

Example 6

Color-changing, light cure Adhesive A was applied by syringe to uppercentral brackets available under the trade designation VICTORY SERIES(Cat. No. 017-401 or equivalent) from 3M Unitek (Monrovia, Calif.) in anamount sufficient to coat the entire base of the bracket when applied toa tooth. The adhesive coated brackets were bonded to bovine teeth usingthe procedure described herein above, resulting in a “wet” toothcondition bond strength of 17.2 MPa with a standard deviation of 7.3 MPa(42.2 pounds per bracket with a standard deviation of 17.8 pounds perbracket).

Using some of the color-changing adhesive coated brackets described inthe paragraph herein above, Transbond MIP adhesive was brushed on thecolor-changing adhesive and then air dried using filtered, drycompressed air to form multi-layer adhesive coated brackets having alayer of Transbond MIP on the precoated color-changing adhesive. Theadhesive layers were dried using filtered, dry compressed air. Themulti-layer adhesive coated brackets were bonded to bovine teeth usingthe procedure described herein above, except that no primer was added tothe tooth prior to bonding, resulting in a “wet” tooth condition bondstrength of 17.9 MPa with a standard deviation of 6.5 MPa (43.9 poundsper bracket with a standard deviation of 16 pounds per bracket).

The “wet” tooth condition bond strength for the multi-layer adhesivecoated bracket illustrates that excellent bond strengths can be obtainedunder “wet” tooth conditions. The “wet” tooth condition bond strengthfor the multi-layer adhesive coated bracket also illustrates thatexcellent bond strengths can be obtained without separately applying aprimer to the tooth. As such, the number of steps required in thetypical orthodontic bonding process may be reduced by eliminating thepriming step.

Example 7

This example illustrates that a continuous layer of self etching primerin a multi-layer adhesive allows elimination of both the etching andpriming steps.

A continuous layer of mono- and di-HEMA phosphates , as described, forexample, in copending U.S. Provisional Patent Application Ser. No.60/494,603, filed Aug. 12, 2003, was applied over a continuous layer ofTransbond XT adhesive in an amount sufficient to coat the entire base ofthe bracket when applied to a tooth. The coated brackets were pressedonto pumiced, unetched, wet bovine teeth and allowed to sit for 60seconds. The flash was then cleaned and the adhesive cured with a3-second exposure mesial and distal with a curing unit available underthe trade designation ORTHO Lite from 3M Unitek (Monrovia, Calif.). Thisresulted in a “wet” tooth condition bond strength of 9.5 MPa with astandard deviation of 2.6 MPa.

The “wet” tooth condition bond strength for the multi-layer adhesivecoated bracket illustrates that excellent bond strengths can be obtainedwithout separately applying a primer to the tooth. As such, the numberof steps required in the typical orthodontic bonding process may bereduced by eliminating the priming and etching steps.

Example 8

The property enhancements described herein are not limited to lightcuring precoat systems. For example, multi-layer chemical cure precoatsystems can provide similar benefits over known chemical cure precoatsystems.

A two part chemical cure adhesive is produced by dispensing alternatingdots of the “A” side and the “B” side on a base of an orthodonticappliance as illustrated in FIG. 6. Separating the two components 34 and36 ensures that they will not cure before application to the tooth.Pressing the adhesive coated bonding base onto a tooth effectively mixesthe two components and allows them to cure. This example shows that achemical cure adhesive system can be delivered to the doctor inprecoated form without requiring the doctor to pretreat the teeth, otherthan cleaning and etching.

Example 9

This example illustrates the preparation of an orthodontic adhesivedelivery system that includes a multi-layer (e.g., a three-layer)adhesive. The orthodontic adhesive delivery system is prepared bydispensing first a thin, low viscosity primer layer onto an adhesivetransfer area of a substrate (e.g., a release liner). The first layerincludes a hydrophilic resin to provide moisture tolerance, and afluoride-releasing agent to provide fluoride release. A second, thickerlayer is applied on top of the first layer. The second has a higherviscosity and higher filler loading than the first layer. The secondlayer also includes an effective concentration of a color changing dye.It also includes a fluoride-releasing agent capable of releasingfluoride. A third, thin, adhesion promoting layer is applied. The thirdlayer includes adhesion promoting agents to enhance adhesion tostainless steel metal brackets. This third layer is also lower viscositythan the second layer. The 3-layer adhesive may then be applied to thebase of a bracket for bonding to a pumiced, etched tooth by positioningthe bracket over the 3-layer adhesive, pushing down slightly to causethe adhesive layers to flow onto the base of the bracket, and lifting upto release the adhesive coated bracket from the adhesive transfer areaof the substrate.

The complete disclosure of all patents, patent applications, andpublications, and electronically available material cited herein areincorporated by reference. The foregoing detailed description andexamples have been given for clarity of understanding only. Nounnecessary limitations are to be understood therefrom. The invention isnot limited to the exact details shown and described, for variationsobvious to one skilled in the art will be included within the inventiondefined by the claims.

1. A packaged article comprising: an orthodontic appliance having a basefor bonding the appliance to a tooth structure; a first hardenableadhesive layer and a second hardenable adhesive layer, each extendingacross at least a portion of the base of the appliance, wherein at leastone of the first or second layers is a patterned layer, and wherein thefirst and second layers differ by one or more properties selected fromthe group consisting of chemical composition, viscosity, hydrophilicity,thickness, curing times, curing mechanisms, color, change in color uponcuring, enzyme release, fluoride release, bond strengths upon curing,filler loading, filler types, and pH, and with the proviso that thefirst and second layers are not in contact with a release substrate; anda container at least partially surrounding the orthodontic appliancehaving the first and second layers thereon.
 2. The packaged article ofclaim 1 wherein the base of the appliance is selected from the groupconsisting of a base flange, a cured single layer adhesive, a curedmulti-layer adhesive, and combinations thereof.
 3. The packaged articleof claim 1 wherein at least one of the first or second layers is anon-patterned layer.
 4. The packaged article of claim 1 wherein at leastone of the first or second layers is selected from the group consistingof primer layers, etchant layers, colored layers, color-changing layers,enzyme releasing layers, fluoride releasing layers, adhesion promotinglayers, and combinations thereof.
 5. The packaged article of claim 1wherein at least one of the first or second layers comprises a componentselected from the group consisting of fluoride releasing agents,adhesive enhancing agents, fillers, micro fillers, enzyme releasingagents, rheology enhancing agents, photobleachable dyes, andcombinations thereof.
 6. The packaged article of claim 1 wherein atleast one of the first or second layers is hardenable by actinicradiation.
 7. The packaged article of claim 6 wherein at least one ofthe first or second layers has an initial color prior to exposure toactinic radiation and a final color that is different from the initialcolor subsequent to the layer being exposed to actinic radiation.
 8. Apackaged article comprising: an orthodontic appliance having a base forbonding the appliance to a tooth structure; a first hardenable adhesivelayer and a second hardenable adhesive layer, each extending across atleast a portion of the base of the appliance, with the proviso that thefirst and second layers are not in contact with a release substrate; oneor more additional hardenable adhesive layers extending across at leasta portion of the first or second layers; and a container at leastpartially surrounding the orthodontic appliance having the first,second, and one or more additional layers thereon.
 9. The packagedarticle of claim 8 wherein at least one of the one or more additionallayers are in contact with a release substrate.
 10. A packaged articlecomprising: a) a substrate with at least one recess with an interiorsurface, b) an orthodontic appliance having a base for bonding theappliance to a tooth structure and having a first hardenable adhesivelayer and a second hardenable adhesive layer, each extending across atleast a portion of the base of the appliance, with the proviso thatneither the first hardenable adhesive layer nor the second hardenableadhesive layer is hardened, and wherein the first and second layersdiffer by one or more properties selected from the group consisting ofchemical composition, viscosity, hydrophilicity, thickness, curingtimes, curing mechanisms, color, change in color upon curing, enzymerelease, fluoride release, bond strengths upon curing, filler loading,filler types, and pH; and c) means for positioning the orthodonticappliance inside the recess such that the adhesive layers do notseparate from the appliance upon removal of the appliance from therecess; d) a cover for the recess; and e) means for maintaining thecover in contact with the substrate, wherein the means for positioningthe orthodontic appliance includes means suspending the appliance in therecess such that the adhesive layers do not contact the interior surfaceof the recess.
 11. A packaged article comprising: an orthodonticappliance having a base for bonding the appliance to a tooth structure,a body extending from the base and at least two opposed tiewingsextending away from the body, the base and at least one of the tiewingsextending past the body in a gingival direction and presenting agingival recess, the base and at least one other of the tiewingsextending past the body in an occlusal direction and presenting anocclusal recess, wherein the appliance has a first hardenable adhesivelayer and a second hardenable adhesive layer, each extending across atleast a portion of the base of the appliance, with the proviso thatneither the first hardenable adhesive layer nor the second hardenableadhesive layer is hardened, and wherein the first and second layersdiffer by one or more properties selected from the group consisting ofchemical composition, viscosity, hydrophilicity, thickness, curingtimes, curing mechanisms, color, change in color upon curing, enzymerelease, fluoride release, bond strengths upon curing, filler loading,filler types, and pH; and a carrier having a pair of arms extendingtoward each other, each of the arms having an outer end section, theouter end sections being spaced apart from each other and presenting achannel therebetween, the orthodontic appliance being located in thechannel and being supported by the arms with one of the outer endsections extending into the occlusal recess and the other of the outerend sections extending into the gingival recess.
 12. An articlecomprising: an orthodontic appliance having a base for bonding theappliance to a tooth structure; and a first hardenable adhesive layerand a second hardenable adhesive layer, each extending across at least aportion of the base of the appliance, with the proviso that neither thefirst hardenable adhesive layer nor the second hardenable adhesive layeris hardened, wherein the first and second layers differ by one or moreproperties selected from the group consisting of chemical composition,viscosity, hydrophilicity, thickness, curing times, curing mechanisms,color, change in color upon curing, enzyme release, fluoride release,bond strengths upon curing, filler loading, filler types, and pH, andwherein at least one of the first or second adhesive layers comprises aphotobleachable dye, and wherein the at least one adhesive has aninitial color prior to exposure to actinic radiation and a final colorsubsequent to exposure to actinic radiation, the initial color beingdifferent than the final color.
 13. The article of claim 12 wherein thebase of the appliance is selected from the group consisting of a baseflange, a cured single layer adhesive, a cured multi-layer adhesive, andcombinations thereof.
 14. The article of claim 12 wherein at least oneof the first or second layers is a patterned layer.
 15. The article ofclaim 12 wherein at least one of the first or second layers is anon-patterned layer.
 16. The article of claim 12 wherein at least one ofthe first or second layers is selected from the group consisting ofprimer layers, etchant layers, colored layers, color-changing layers,enzyme releasing layers, fluoride releasing layers, adhesion promotinglayers, and combinations thereof.
 17. The article of claim 12 wherein atleast one of the first or second layers comprises a component selectedfrom the group consisting of fluoride releasing agents, adhesiveenhancing agents, fillers, micro fillers, enzyme releasing agents,rheology enhancing agents, photobleachable dyes, and combinationsthereof.
 18. The article of claim 12 wherein at least one of the firstor second layers is hardenable by actinic radiation.
 19. The article ofclaim 12 wherein at least one of the first or second layers furthercomprises a hardener comprising a sensitizing compound different fromthe photobleachable dye.
 20. The article of claim 12 wherein the changein color from the initial color to the final color has a ΔE* of greaterthan
 10. 21. The article of claim 12 wherein the change in color fromthe initial color to the final color has a ΔE* of greater than
 15. 22.The article of claim 12 wherein the change in color from the initialcolor to the final color has a ΔE* of greater than
 20. 23. A method ofbonding an orthodontic appliance to a tooth structure comprising:providing an article according to claim 12; applying the base of theappliance to the tooth structure; and exposing the adhesive to actinicradiation.
 24. An article comprising: an orthodontic appliance having abase for bonding the appliance to a tooth structure; a first hardenableadhesive layer and a second hardenable adhesive layer, each extendingacross at least a portion of the base of the appliance, with the provisothat neither the first hardenable adhesive layer nor the secondhardenable adhesive layer is hardened; and one or more additionalhardenable adhesive layers extending across at least a portion of thefirst or second layers, wherein at least one of the first or secondadhesive layers comprises a photobleachable dye, and wherein the atleast one adhesive has an initial color prior to exposure to actinicradiation and a final color subsequent to exposure to actinic radiation,the initial color being different than the final color.
 25. An articlecomprising: an orthodontic appliance having a base for bonding theappliance to a tooth structure; a first hardenable adhesive layerextending across at least a portion of the base of the appliance andcovering a first area; and a second hardenable adhesive layer extendingacross at least a portion of the base of the appliance and covering asecond area, wherein the second area is different than the first area,wherein the first and second layers differ by one or more propertiesselected from the group consisting of chemical composition, viscosity,hydrophilicity, thickness, curing times, curing mechanisms, color,change in color upon curing, enzyme release, fluoride release, bondstrengths upon curing, filler loading, filler types, and pH, and whereinat least one of the first or second layers is a patterned layer.
 26. Thearticle of claim 25 wherein the first area is coextensive with the baseof the appliance.
 27. The article of claim 26 wherein the second area issmaller than the first area.
 28. The article of claim 27 wherein thesecond area is proximate the center of the base of the appliance. 29.The article of claim 25 further comprising: one or more additionalhardenable adhesive layers extending across at least a portion of thefirst or second layers.
 30. The article of claim 25 wherein at least oneof the first or second layers is a non-patterned layer.
 31. The articleof claim 25 wherein at least one of the first or second layers isselected from the group consisting of primer layers, etchant layers,colored layers, color-changing layers, enzyme releasing layers, fluoridereleasing layers, adhesion promoting layers, and combinations thereof.32. The article of claim 25 wherein at least one of the first or secondlayers comprises a component selected from the group consisting offluoride releasing agents, adhesive enhancing agents, fillers, microfillers, enzyme releasing agents, rheology enhancing agents,photobleachable dyes, and combinations thereof.
 33. The article of claim25 wherein at least one of the first or second layers is hardenable byactinic radiation.
 34. The article of claim 33 wherein at least one ofthe first or second layers has an initial color prior to exposure toactinic radiation and a final color that is different from the initialcolor subsequent to the layer being exposed to actinic radiation.
 35. Amethod of bonding an orthodontic appliance to a tooth structurecomprising: providing an article according to claim 25; applying thebase of the appliance to the tooth structure; and exposing the adhesiveto actinic radiation.
 36. A method of preparing a precoated orthodonticappliance comprising: providing an orthodontic appliance having a basefor bonding the appliance to a tooth structure; disposing a firsthardenable adhesive layer on at least a portion of the base of theappliance; and disposing a second hardenable adhesive layer on at leasta portion of the base of the appliance, with the proviso that neitherthe first hardenable adhesive layer nor the second hardenable adhesivelayer is hardened, wherein the first and second layers differ by one ormore properties selected from the group consisting of chemicalcomposition, viscosity, hydrophilicity, thickness, curing times, curingmechanisms, color, change in color upon curing, enzyme release, fluoriderelease, bond strengths upon curing, filter loading, filler types, andpH, and wherein at least one of the first or second layers is apatterned layer.
 37. The method of claim 36 wherein disposing at leastone of the adhesive layers comprises printing or dispensing the at leastone layer.
 38. A method of preparing a precoated orthodontic appliancecomprising: providing an orthodontic appliance having a base for bondingthe appliance to a tooth structure; disposing a first hardenableadhesive layer on at least a portion of the base of the appliance;disposing a second hardenable adhesive layer on at least a portion ofthe base of the appliance; and applying a release substrate on at leastone of the adhesive layers, wherein the first and second layers differby one or more properties selected from the group consisting of chemicalcomposition, viscosity, hydrophilicity, thickness, curing times, curingmechanisms, color, change in color upon curing, enzyme release, fluoriderelease, bond strengths upon curing, filler loading, filler types, andpH.